Plant cell wall polysaccharides constitute 90% of the plant cell wall and can be divided into three groups: cellulose, hemicellulose, and pectin. Cellulose represents the major constituent of cell wall polysaccharides. Hemicelluloses are the second most abundant constituent of plant cell walls. The major hemicellulose polymer is xylan. The biodegradation of the xylan backbone depends on two classes of enzymes: endoxylanases and beta-xylosidases. Endoxylanases (EC 3.2.1.8) cleave the xylan backbone into smaller oligosaccharides, which can be further degraded to xylose by beta-xylosidases (EC 3.2.1.37). Other enzymes involved in the degradation of xylan include, for example, acetylxylan esterase, arabinase, alpha-glucuronidase, esterase, and p-coumaric acid esterase.
WO02/12472 disclosed esterase which is capable of stereoselective hydrolysis of chiral esters and of hydrolyzing ferulic acid esters.
Faulds and Williamson, 1991, J. Gen. Microbiol. 137 2339-2345, describe the purification and characterization of 4-hydroxy-3-methoxy-cinnamic (ferulic) acid esterase from Streptomyces olivochromogenes. Faulds and Williamson, 1994, Microbiology 140 779-787, describe the purification and characterization of a feruloyl esterase from Aspergillus niger. Kroon et al., 1996, Biotechnol. Appl. Biochem. 23 255-262, describe the purification and characterisation of a novel esterase induced by growth of Aspergillus niger on sugarbeet pulp. deVries et al., 1997, Appl. Environ. Microbiol. 63 4638-4644, disclose the esterase genes from Aspergillus niger and Aspergillus tubingensis. Castanares et al., 1992, Enzyme Microbiol. Technol. 14 875-884, describe the purification and properties of a feruloyl/p-coumaroyl esterase from the fungus Penicillium pinophilum. 
The present invention relates to polypeptides having esterase activity and polynucleotides encoding the polypeptides.